This invention relates generally to atmospheric gas burners, particularly to gas burners for domestic cooking appliances. The invention more specifically relates to improvements in gas burners for reducing flame instability.
Atmospheric gas burners are commonly used as surface units in household gas cooking appliances. A significant factor in the performance of such gas burners is their ability to withstand disturbances in the surroundings, such as room drafts or oven door slams. Manipulation of the oven door can be particularly troublesome because opening and closing of the oven door produces a momentary under-pressure and over-pressure, respectively, in the oven cavity. This causes a temporary condition in which a flow of air is required to reequilibrate the oven pressure. Since the flue through which combustion products are removed from the oven is sized to maintain the desired oven temperature and is thus generally inadequate to supply a sufficient air flow for reequilibration, a large amount of air passes through or around the burners.
This surge of air is detrimental to the flame stability of the burners and can even cause extinction of the flames. Unwanted flame extinction not only presents an obvious quality concern but also creates a potential safety hazard in that unburned gas will be emitted from the burner after the disturbance passes. The problem is particularly evident in the so-called sealed gas burner arrangements (referring to the lack of an opening in the cooktop surface around the base of the burner to prevent spills from entering the area beneath the cooktop), and while the burners are operating near their minimum input rate.
The inherent cause of this flame instability is the low pressure drop of the gas/air mixture passing through the burner ports of a typical rangetop burner. Although there is ample pressure available in the fuel, the pressure energy is used to accelerate the fuel to the high injection velocity required for primary air entrainment. Relatively little of this pressure is recovered at the burner ports. A low pressure drop across the ports allows pressure disturbances propagating through the ambient to easily pass through the ports, momentarily drawing the flame towards the burner head and leading to thermal quenching and extinction.
Accordingly, there is a need for an atmospheric gas burner which is better able to withstand ambient pressure disturbances.